Fibrous 2-phosphatoethyl ethers of cellulose and process of making the same



2,743,232 rupnous Z-PHOSPHATOETHYL mnnnson cm.-

il -leans, La., assiguors to the United States of America ,as represented by the Secretary of Agriculture No Drawing. Application July 18, 1952,

Serial No. 299,771

4 Claims. (Cl. 8-120 (Granted under Title 35, U. S. Code (1952), sec. 266) .A non-exclusive, irrevocable, royalty-free license in the invention herein described, for all governmental purposes, throughout the world, with the power to grant sublicenses for such purposes, is hereby granted to the Goveriiment of the United States of America.

This invention relates to partial ethers of fibrous cellulose in which the fibrous form and the propertieslit produces in textiles, i. e., properties such as handffeel, tensile strength and the like are retained substantially unaltered. The invention provides: fibrous 2-phospha'toethylpartial ethers of cellulose; the salts of such ethers; and a process or reducing; the combustibility of fibrous cellulosic materials. Y i I We have discovered that bringing a cellulosic material containing hydroxyl groups into contact with a solution consisting of an alkali'metal salt of 2-chloroethylphosphoric acid (Z-chloroethyl dihydrogen phosphate) and unreacted alkali metal hydroxide dissolved in water, at a temperature at which reaction takes place results in a conversion of hydroxyl groups of the cellulosic material to 2-phosphatoethyl groups (O CH zC I-I 20P,Oa=,), and

7 that little saponification of the chloroethyl phosphate takes place. According to this invention, fibrous alkali metal salts of 2-phosphatoethyl partial ethers of cellulose are produced by reacting fibrous cellulosic materials containing hydroxyl groups with an aqueous solution of alkali metal salt of 2-.chloroethylphosphori c acid (or other salts of .Z-chloroethylphosphoric acid may be used in which the alkali metal will replace the cations of the Salt): and anex'c'ess of alkali metal hydroxide. The corresponding dibasic acid esters are produced by contactingthe fibrous alkali metal salts thus produced with a dilute aqueous strong mineral acid until substantially all of the alkali metal atoms have been replaced by hydrogen atoms.

The combustibility of fibrous cellulosic materials coni .tain ing hydroxyl groups are reduced by converting the cellulosic materials to the corresponding dibasic acid ethers in the above manner and contacting such ethers with ammonia until substantially one equivalent of amrnonia per mole of phosphorus has been neutralized, the

withNl-h groups.

".Substan tially any fibrous cellulosic material, which contains hydroxyl. groups and which can be merceriz ed, can be phosphatoethylated by the process of this invention. .Suitablecellulosic materials include: cotton fibers, regenerated cotton fibers, aminized cotton fibers, carboxymethylated cotton fibers, paper, and the likematerials. The use of cotton fibers is preferred. The fibrous cellulosic materials can be phosphatoethylv ated in the form of free fibers, sliver, yarn, or fabric.

The use of fabric is preferred.

The alkali metal salt of Z-chloroethylphosphoric acid for use in the invention can be preparedby a varietyof knownprocedures. One method comprises: preparing 2'- chloroethylp'hosphoryl dichloride by the method of Kenshaw and' HopkinsJ. Chem. Soc. 51.1953 4, b e-re States Patent cellulosic material becomes appreciable.

ice

2 lycing the dichloride with water and reacting the resultant acid with an alkali metal. The substantially neutral sodium or potassium salts of 2-chloroethylphosphoric acid are particularly suitable. I I

Aqueous solutions of the alkali metal or other salts of 2-chloroethylphosphoric acid and excess or unreacted alkali metal hydroxide suitable for use in the present process can be aqueous solutions of the salt and any alkali metal hydroxide containing from about 8 to 25% by weight unreacted alkali metal hydroxide and from about 5 to 15% by weight of the alkali metal salt of 2-'ch loroethylphosphoric acid. Aqueous solutions of the sodium salt of the acid containing from about 14 to 20% unreacted sodium hydroxide and from about 10 to 12% of the sodium salt of the acid are preferred.

The fibrous cellulosic material can be reacted with such aqueous solutions in a variety of manners. For example, the cellulosic material can be impregnated with an aqueous solution of 2-chloroethylphosphoric acid, or any' soluble salt thereof, followed by an impregnation of the resultant wet fabric with an aqueous solution of an alkali metal hydroxide; using, in each step, solution concentrations and solution pick-ups of such magnitude that the resultant aqueous solution which is finally in contact with'the fabric contains organoph0$phate anions and unreacted alkali metal hydroxide in about the indicated proportions. Alternatively the cellulosic material can be impregnated with a solution consisting of 2-chloroethylphosphoric acid, or a soluble salt thereof, dissolved along with an alkali metal hydroxide in water to make a solution containing about the indicated proportions of unreacted alkali metal hydroxide and the acid. ,The latter method is preferred. i

The impregnation of the fibrous cellulosic material can be accomplished by any of the conventional procedures for impregnating such materials with solutions; for example, by the procedures for impregnating such materials with mercerizing solutions. The use of a textile padder in the impregnation step is preferred.

The reaction can be conducted at temperatures ranging from about room temperature (i. e., about 20 C.) to temperatures at wh'ich the thermal decomposition of the Cotton fabric is preferably padded with an aqueous solution containing the organophosphate anions and unreacted alkali metal hydroxide to a pick-up of from about to 150% and heated at from about 80 to C. for from about 5 to 40 minutes, using a shorter time witha higher temperature.

The impregnated fibrous cellulosic material can be heated in the conventional textile material heating apparatus such as ovens, hot boxes, steam heated cans and the like. After thedesired extent of reaction is completed, fibrous cellulosic material is preferably washed free of any excess reactants and-dried by a conventionaltextilt"v d' d Washin with water nd ir dr n acld hydrogens of the dlbastc acid esters being replaced rymg proce ure g a g The ,phosphatocthylation processproduces an alkali metal saltof a fibrous 2-.phcsphatoethyl partial ether of cellulose. These ether products are valuable cationexchange materials. For example, cotton fabrics phosphatoetllylated,,using a sodium salt of 2 -chloroethylphosphoric acid in the Pr ence o a e-acted s d m y xid constitut ion exchange fabrics in the sodium cycle of the ion ex.- chaageprocess, By the conventionalprocedures of ion exchange, such fabrics can be converted-to the hydrogen cycle and the hydrogen atoms can be replaced by substantially any cation dissolved in an aqueous medium. In such ethers the phosphorus is bound to the molecules of cellulose by relatively strong bnnds. For example, when a phosphatoethylated cotton fabric is subjected to the Numbet 4 wash t'est of the American Association of Textile Chemists and Colorists, it undergoes no reduction in phosphorus content.

Fibrous dibasic 2-phosphatoethyl partial ethers of cellulose are preferably prepared. by contacting the alkali metal salts of fibrous 2-phosphatoethyl cellulosic materials with a dilute aqueous solution of a strong inorganic acid. The use of aqueous solutions containing from about 3 to of acids such as hydrochloric orsulfuric acid is preferred. The contact is preferably maintained until substantially all of the alkali metal atoms have been replaced by hydrogen atoms as determined by immersion in standard base and back-titration with standard acid.. The resultant dibasic acid ethers are preferably washed free of excess reactants. Water washing is preferred. Such fibrous dibasic acid ethers exhibit a marked resistance to burning when they contain about 2% or more of phosphorus and they constitute valuable cellulosic materials which are capable of reacting with many compounds by the typical reactions of organic monoesters of phosphoric acid. Such fibrous dibasic acid ethers are relatively stable compounds, but when they are dried andstored for several weeks the fiber strength decreases markedly.

The combustibility of fibrous cellulosic materials is preferably reduced by treating the materials in the form of fabrics. The treatment is preferably applied to cotton fabrics. The fabric is preferably phosphatoethylated to a phosphorus content of at least about 0.25%. Much higher phosphorus contents can be used in producing fabrics for many applications although fabrics containing more than about 2.5% phosphorus tend to become stiff and boardy. The resultant alkali metal salts are preferably converted to the dibasic acid form and contacted with an aqueous solution containing fromabout 2 to 5% of ammonia until substantially one equivalent of ammonia per mole of phosphorus has been neutralized. Alternatively, the acid form of the phosphatoethylated cellulosic materials can be contacted with gaseous ammonia or with a solution containing unreacted ammonia.

Even when cellulosic material contains as little as 0.25% phosphorus, the ammonium salts of such fibrous materials exhibit a reduced combustibility. In addition, when they do burn, they produce a black char which exhibits no afterglow. Since the production of such achar and the lack of afterglow are important characteristics of a flameproofed fabric, the present process can advantageously be used as a supplement to other flameproofing processes to enhance the char and afterglow characteristics of the flameproofed fabric. Ammonium salts of phosphatoethylated fibrous cellulosic materials containing at least about 2% phosphorus will not burn even when materials composed of such fibers are held in a vertical position and lighted at the bottom.

Thus the produced chemically modified textile fibers are modified only in that a plurality of the hydroxyl groups of the cellulose contained in the fibers are converted to OCHzCI-IzOPOzMz groups in which M is hydrogen or NH4. The degree of conversion is such that the modified cotton has about 0.25 to 2.5 phosphorus contained in the OCHzCHzOPOaMz group. p

The following examples are illustrative of the invention.

Combustibility tests-The cloths prepared in the following examples were cut into strips 1 cm. wide and at least 5 cm. long. The strips were held with their surface vertical and their long edge at the indicated angle from the vertical and ignited at the specified point. Whether or not the burning would continue along the strip and the presence or absence of afterglow were observed; Strips of the cloths used in each of the examples, prior to treatment, would burn continuously even when held vertically and ignited at the top.

EXAMPLE 1 I Phosphatoeihylation Cotton print cloth was padded with a solutionconsist- 'ing about 33%.organophosphate anions.

ing of: 150 parts sodium salt of 2-chloroethylphosphoric acid, 850 parts aqueous 25 sodium'hydroxide, and 200 parts water. (Solution pick-up was 136%.) cloth was heated at 110 C. for 18 minutes, padded with aqueous 25% sodium hydroxide (pick-up heated at 10 C. for 30 minutes, Washed and dried.

v The cloth contained 1.34% phosphorus and 11.1%v moisture. After laundering (AATCC 36-45 No. 4 teste using 0.5% soap, 0.2% sodium carbonate, and 0.1% chlorine at 182 F for 45 min.) the cloth contained 1.32% phosphorus and 10.4% moisture.

A sample of the same cloth after boiling forj6 hours in 1% sodium hydroxide solution contained 1.36% phosphorus and 9.0% moisture.

A strip of the cloth held at an angle of 90 from the vertical and lighted at one end burned continuously, but a strip held at 45 from the vertical and lighted at the upper end would not burn continuously. ,The strips ex hibited some afterglow.

Ammonium salt production A portion of the cloth converted to the ether sodium continuously. The strip exhibited no afterglow.

EXAMPLE 2 Separate application of 2-chloroethylphosphoric acid Cottom print cloth was impregnated with aqueous 18% sodium hydroxide, allowed to stand for 15 minutes, and then impregnated with a solution consisting of water and a neutral sodium salt of 2-chloroethylphosphate contain- The wet cloth was heated at C. for v15 minutes, cooled, re-impregnated with the acidsalt, heated at 110 C. for 35 minutes, washed, and dried.

The clothhad a cation exchange capacity of 1.5 milliequivalents per gram and contained 2.68% phosphorus.

After material prepared above was acidified and converted to the ammonium salt by the procedure described in Example'l, a strip of the cloth held vertically and lighted at the bottom would not burn continuously. No afterglow was observed.

EXAMPLE 3 Reaction at room temperature Cotton print cloth was impregnated with aqueous "18% sodium hydroxide, twice impregnated with a solution consisting of water and a neutral sodium salt of 2-chloroethylphosphoricacid containing about 33% organophosphate anions and allowed to stand for 6.5 days'at room temperature.

The cloth exhibited a cation exchange capacityof 1.7

Curing times and temperatures in relation to combined phosphorus Cotton print cloth was impregnated with a solution consisting of water, sodium hydroxide and a sodium salt of 2-chloroethylphosphoric acid containing 10% unreacted sodium. hydroxide and 20% organophosphate anions (132% pick-up). Portions of the wet cloth were heated V The wet Cation-exchange capacity in milliequiv. per g. (dry basis) Phosphorus content in percent (dry basis) Curing time 80 90 100 110 80 100 110 C. O. C. C. C. O. C. C.

EXAMPLE Unreacted alkali metal hydroxide concentration in relation to combined phosphorus Samples of cotton print cloth were padded with solutions of sodium salt of 2-chloroethylphosphoric acid, sodium hydroxide and water containing 10% organophosphate anions and the indicated amounts of unreacted sodium hydroxide (130% average pick-up). The wet cloths were heated for 20 minutes at 100 C., washed and air dried.

The cation exchange capacities and phosphorus content of the so treated cloths are expressed in the following table.

Chloroethyl phosphate acid anion concentration in relation to combined phosphorus Samples of cotton print cloth were padded with a solution of the sodium salt of 2-chloroethylphosphoric acid, sodium hydroxide and water containing 16% unreacted sodium hydroxide and the indicated amounts of organophosphate anions (130% average pick-up). The wet cloths were heated 20 minutes at 100 C., washed and 7 air dried.

The cation exchange capacities and the phosphorus content of the so treated cloths are indicated in the following table.

Cation- Pereent 2-chloroethyl phosphoric acid exchange (21- Percent anions pacity, milli- Phosphorus equiv. per g.

EXAMPLE 7 Repeated phosphatoethylation Cotton print cloth was padded with a solution of sodium salt of 2-chloroethylphosphoric acid, sodium hydroxide and water, containing 16% unreacted sodium hydroxide and 10% organophosphate anions 130% pick-up), heated for 20 minutes at 100 C., washed and dried. The resultant cloth had a cation exchange capacity of 0.80 milliequivalents per g. and a phosphorus content of 1.34%.

The cloth was re-treated in the above manner. It then had a cation exchange capacity of 1.5 milliequivalents per g. and a phosphorus content of 2.4%.

The re-treated cloth was converted to the ammonium salt by the process of Example 1. A strip of the so treated cloth held vertically and lighted at the bottom would not support combustion. No afterglow was observed.

We claim:

A process comprising impregnating a cotton fabric with an aqueous solution of about 5 to 15% by weight of a sodium salt of 2-chloroethylphosphoric acid and about 14 to 20% by weight of sodium hydroxide, and heating the wet fabric at about 80 to 110 C. for

about 5 to 40 minutes, using a shorter time with a higher temperature to produce a modified cotton having about 0.25 to 2.5% phosphorus by weight.

.2. A process comprising impregnating a cotton fabric with an aqueous solution of about 5 to 15% by weight of a sodium salt of 2-chloroethylphosphoric acid and about 14 to 20% by weight of sodium hydroxide, heating the wet fabric at about to C. for about 5 to 40 minutes, using a shorter time with a higher temperature to produce a modified cotton that has about 0.25 to 2.5% phosphorus by weight, and contacting the resultant fabric with a hydrochloric acid solution to replace substantially all of the sodium atoms with hydrogen atoms.

3. A process comprising impregnating a cotton fabric with an aqueous solution of about 5 to 15% by weight of a sodium salt of 2-chloroethylphosphoric acid and about 14 to 20% by weight of sodium hydroxide, heating the wet fabric at about 80 to 110 C. for about 5 to 40 minutes, using a shorter time with a higher temperature to produce a modified cotton that has about 0.25 to 2.5% phosphorus by weight, contacting the resultant fabric with a hydrochloric acid solution to replace the sodium atoms with acid hydrogen atoms, and contacting the resultant fabric with an ammonium hydroxide solution to replace the acid hydrogens with NH4 groups.

4. Chemically modified cotton textile fibers modified only in that a sufficient number of hydroxyl groups of the cellulose contained therein have been converted to -OCH2CH2OPO3M2 groups in which M is selected from the group consisting of hydrogen and NII-t, the degree of conversion being such that the modified cotton contains about 0.25 to 2.5 by Weight phosphorus contained in the OCH2CH2OPO3M2 groups, has reduced combustibility, and has a cation exchange capacity of 0.15 to 1.5 milliequivalents per gram.

References Cited in the file of this patent UNITED STATES PATENTS 2,256,380 Dickey et al. Sept. 16, 1941 2,265,585 Urbain et a1 Dec. 9, 1941 FOREIGN PATENTS 837,592 France Feb. 14, 1939 343,873 Great Britain Feb. 16, 1931 OTHER REFERENCES Reid et al.: Ind. and Eng. Chemistry, vol. 41, #12, pp. 2828-2834, Dec. 1949. 

1. A PROCESS COMPRISING IMPREGNATING A COTTON FABRIC WITH AN AQUEOUS SOLUTION OF ABOUT 5 TO 15% BY WEIGHT OF A SODIUM SALT OF 2-CHLOROETHYLPHOSPHORIC ACID AND ABOUT 14 TO 20% BY WEIGHT OF SODIUM HYDROXIDE, AND HEATING THE WET FABRIC AT ABOUT 80 TO 110* C. FOR ABOUT 5 TO 40 MINUTES, USING A SHORTER TIME WITH A HIGHER TEMPERATURE TO PRODUCE A MODIFIED COTTON HAVING ABOUT 0.25 TO 2.5% PHOSPHOROUS BY WEIGHT.
 4. CHEMICALLY MODIFIED COTTON TEXTILE FIBERS MODIFIED ONLY IN THAT A SUFFICIENT OF HYDROXYL GROUPS OF THE CELLULOSE CONTAINED THEREIN HAVE BEEN CONVERTED TO -OCH2CH2OPO3M2 GROUPS IN WHICH M IS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN AND NH4, THE DEGREE OF CONVERSION BEING SUCH THAT THE MODIFIED COTTON CONTAINS ABOUT 0.25 TO 2.5% BY WEIGHT PHOSPHORUS CONTAINED IN THE -OCH2CH2OPO3M2 GROUPS, HAS REDUCED COMBUSTIBILITY, AND HAS A CATION EXCHANGE CAPACITY OF 0.15 TO 1.5 MILLIEQUIVALENTS PER GRAM. 